ROCK TUMBLING is not an exact science. It takes some patience and alot of cleanliness to be sucessful. Here are my personal tips on rock tumbling. Hopefully this guide prevent the novice from making simple mistakes.
First off this guide is for rotary tumblers. Usually you run 4 steps for a total of four weeks.
Step 1 is usually a 60/90 mixture of silicon carbide grit. A three pound rock tumbler would be filled three quarters of the way to the top with rocks, water is added to just below the rock level and 4 ounces of silicon carbide would be added. This runs continously for one week. Be sure to check for leaks during the week.
Step 2 is usually 220 silicon carbide grit. A three pound rock tumbler would require 3.5 ounces of grit. Again add water and run for one week as in step 1.
Step 3 is usually 500 silicon carbide grit. A three pound rock tumbler would require 3 ounces of grit. Again add water and run for one week as in step 1.
Step 4 is a polish. A three pound rock tumbler would require 2.5 ounces of polish. Again add water and run for one week as in step 1.
The quality of the material that you are tumbling will make a difference in the outcome. Garbage In, Garbage Out. You will have much more success if you have nice colored stones to start with. Stones that are full of holes and cracks are much harder to clean between grit changes.
Cleaning between grits is probably the most time consuming part of tumbling rocks. However it is one of the most important things to do properly. You must clean all of the grit off of each stone and out of the barrel before proceeding to the next finer grit. If you don't you will prolong the time it takes to tumble. The little piece of grit you miss will keep on working -- scratching until it eventually breaks down to a smaller and smaller size.
Do not clean out your tumbler in the sink. Washing the slurry down your drains will lead to clogged drains. I use a spaghetti strainer and a trash can, after everything drains into the trash can I let the water evaporate and then throw whats left into the garbage.
Be sure to inspect each rock and you will usually find some that have a little slurry that didn't wash off. Scrub these with a toothbrush to loosen grit and rinse. When you are through, then clean the barrel. Be sure to thoroughly scrub the barrel for the next grit size. It's alot of work , but I don't know of any easy way to do this part of the job.
The types of rock in a batch can cause problems that won't show up until you try to polish. These may be due to different hardnesses. It's a good idea to separate stones by hardness before you begin. This can be done with a simple scratch test. Scratch the different types of stones against one another, if one stone really scratched another they should not be in the same batch. A Covington Engineering double barrell rock tumbler is a very nice machine as you can run two batches of different hardnesses at the same time.
I hope this little guide assists in your rock tumbling adventures. (deb)